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United States Patent |
6,076,373
|
Grodziski
|
June 20, 2000
|
Apparatus and method for bending glass sheets
Abstract
The present invention provides an apparatus and method for a shaping sheet
including a support frame and a shaping rail supported on the frame. The
shaping rail has a sheet shaping surface that conforms in elevation and
outline to a final desired shape of a marginal edge of a glass sheet to be
shaped. An auxiliary rail having a sheet shaping surface which generally
corresponds to a preliminary shape of a selected marginal edge portion of
the sheet is positioned along a section of the shaping rail having a sheet
shaping surface portion which generally corresponds to the final desired
shape of the selected marginal edge portion of the sheet. The auxiliary
rail is mounted for movement relative to the shaping rail section from a
first position, wherein portions of the sheet shaping surface of the
auxiliary rail are above the sheet shaping surface portion of the shaping
rail section, and a second position wherein the sheet shaping surface of
the auxiliary rail is positioned below the sheet shaping surface portion
of the shaping rail section. When the auxiliary rail is in its first
position, it is capable of supporting the selected marginal edge portion
of the sheet above the shaping rail section and preliminarily shaping the
sheet. When the auxiliary rail is in its second position, the sheet
shaping surface portion of the shaping rail section is capable of
supporting and shaping the selected marginal edge portion of the sheet to
the final desired shape.
Inventors:
|
Grodziski; Zenon (Aniche, FR)
|
Assignee:
|
PPG Industries Ohio, Inc. (Cleveland, OH)
|
Appl. No.:
|
876872 |
Filed:
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June 16, 1997 |
Current U.S. Class: |
65/107; 65/287; 65/289; 65/290; 65/291 |
Intern'l Class: |
C03B 021/00; C03B 023/00; C03B 023/02; C03B 025/00 |
Field of Search: |
65/106,107,273,287,289,290,291
|
References Cited
U.S. Patent Documents
2452488 | Oct., 1948 | Paddock et al.
| |
2554572 | May., 1951 | Jendrisak.
| |
2608039 | Aug., 1952 | Jendrisak | 49/67.
|
2695476 | Nov., 1954 | Jendrisak.
| |
2702445 | Feb., 1955 | Jendrisak.
| |
2920423 | Jan., 1960 | Carson et al. | 49/67.
|
3235350 | Feb., 1966 | Richardson | 65/107.
|
3269822 | Aug., 1966 | Carson et al.
| |
3356480 | Dec., 1967 | Golightly.
| |
3511628 | May., 1970 | Adamson.
| |
4047916 | Sep., 1977 | Reese et al. | 65/106.
|
4119424 | Oct., 1978 | Comperatore | 65/107.
|
4203751 | May., 1980 | Roth et al. | 65/106.
|
4265650 | May., 1981 | Reese et al. | 65/104.
|
4286980 | Sep., 1981 | Matsuzaki | 65/106.
|
4596592 | Jun., 1986 | Frank.
| |
4606749 | Aug., 1986 | Nushi et al. | 65/106.
|
4626267 | Dec., 1986 | Reese et al. | 65/106.
|
4741751 | May., 1988 | Claassen et al.
| |
4804397 | Feb., 1989 | Stas et al. | 65/107.
|
4894080 | Jan., 1990 | Reese et al. | 65/106.
|
5049178 | Sep., 1991 | Pereman et al. | 65/106.
|
5087281 | Feb., 1992 | Kakino et al. | 65/290.
|
5167689 | Dec., 1992 | Weber | 65/106.
|
5186730 | Feb., 1993 | Weber | 65/289.
|
5383990 | Jan., 1995 | Tsuji | 156/102.
|
5660609 | Aug., 1997 | Muller et al.
| |
5849057 | Dec., 1998 | Didelot | 65/106.
|
Foreign Patent Documents |
0 640 569 | Mar., 1995 | EP.
| |
0 705 798 | Apr., 1996 | EP.
| |
96/12682 | May., 1996 | WO.
| |
Primary Examiner: Silverman; Stanley S.
Assistant Examiner: Ruller; Jacqueline A.
Attorney, Agent or Firm: Siminerio; Andrew C., Lepiane; Donald C.
Claims
What is claimed is:
1. An apparatus for shaping a glass sheet, comprising:
a support frame;
a shaping rail supported on said frame the shaping rail having (1) a pair
of spaced elongated members defined as a center section, each of the
spaced members of the center section having a longitudinal axis extends in
a first direction and being secured in a fixed position on said frame and
(2) having a pair of movable shaping rail sections defined as a first
movable shaping rail section and a second movable shaping rail section the
first movable shaping rail section mounted adjacent one end of the center
section and the second movable shaping rail mounted adjacent the other end
of the center section the first and second rail sections are pivotally
mounted for movement toward said support frame to a first position and
away from said support frame to a second position wherein when the movable
shaping rail sections are in the second position the shaping rail has a
sheet shaping surface that conforms in elevation and outline to a final
desired shape of a marginal edge of a glass sheet to be shaped; and
at least one elongated auxiliary rail having a longitudinal axis, the at
least one auxiliary rail having a sheet shaping surface, positioned
adjacent one of the movable shaping rail sections of said shaping rail,
wherein said movable shaping rail section has a sheet shaping surface
portion generally corresponding to said final desired shape of a selected
marginal edge portion of the sheet to be shaped, said auxiliary rail
mounted for movement relative to said movable shaping rail section between
a first position, and a second position such that the longitudinal axis of
said auxiliary rail is transverse to the longitudinal axis of the
elongated member of the center section, wherein when said auxiliary rail
and said moveable shaping rail sections are each in their first position,
portions of said sheet shaping surface of said auxiliary rail are above
said sheet shaping surface portion of said movable shaping rail section
and wherein when said auxiliary rail and said moveable shaping rail
sections are each in their second position, said sheet shaping surface of
said auxiliary rail is below said sheet shaping portion of said movable
shaping rail section.
2. The apparatus as in claim 1 wherein said movable shaping rail section is
mounted for pivotal movement from its first position to its second
position and said auxiliary rail has a sheet shaping surface generally
corresponding to a preliminary shape of said selected marginal edge
portion of said sheet.
3. An apparatus for shaping a glass sheet, comprising:
a support frame;
a shaping rail supported on said frame and having a movable shaping rail
section, said movable shaping rail mounted for pivotal movement toward
said support frame to a first position and away from said support frame to
a second position wherein when the movable shaping rail section is in the
second position the shaping rail has a sheet shaping surface that conforms
in elevation and outline to a final desired shape of a marginal edge of a
glass sheet to be shaped; and
at least one auxiliary rail having a sheet shaping surface generally
corresponding to a preliminary shape of said selected marginal edge
portion of said sheet, positioned adjacent the movable shaping rail
section of said shaping rail, wherein said movable shaping rail section
has a sheet shaping surface portion generally corresponding to said final
desired shape of a selected marginal edge portion of the sheet to be
shaped, said auxiliary rail mounted at one end for movement relative to
said movable shaping rail section pivotally between a first position, and
a second position wherein when said auxiliary rail and said moveable
shaping rail are each in the first position, portions of said sheet
shaping surface of said auxiliary rail are above said sheet shaping
surface portion of said movable shaping rail section and wherein when said
auxiliary rail and said moveable shaping rail are each in the second
position, said sheet shaping surface of said auxiliary rail is below said
sheet shaping portion of said movable shaping rail section.
4. The apparatus as in claim 1 further including an auxiliary rail support
arrangement mounted on said frame for movement from a first position,
wherein said support arrangement supports said auxiliary rail at said
auxiliary rail's first position, to a second position wherein said support
arrangement allows said auxiliary rail to drop from said auxiliary rail's
first position to its second position.
5. The apparatus as in claim 1 further including lifters to vertically
reciprocate said auxiliary rail between its first and second positions.
6. The apparatus as in claim 1 wherein said sheet shaping surface of said
auxiliary rail has a straight profile.
7. The apparatus as in claim 6 wherein said auxiliary rail is positioned
outboard of said movable shaping rail section and said sheet shaping
surface of said auxiliary rail is completely above said sheet shaping
surface portion of said movable shaping rail section when said auxiliary
rail and said movable shaping rail section are each at their first
position.
8. The apparatus as in claim 7 further including an auxiliary rail support
arrangement mounted on said frame for movement from a first position,
wherein said support arrangement supports said auxiliary rail at said
auxiliary rail's first position, to a second position wherein said support
arrangement allows said auxiliary rail to drop from said auxiliary rail's
first position to its second position.
9. The apparatus as in claim 1 wherein said auxiliary rail has a horizontal
curvature that generally corresponds to a horizontal curvature of said
movable shaping rail section.
10. The apparatus as in claim 1 wherein said auxiliary rail is positioned
outboard of said movable shaping rail section.
11. The apparatus as in claim 1 wherein said auxiliary rail is positioned
inboard of said movable shaping rail section.
12. The apparatus as in claim 1 wherein said sheet shaping surface of said
auxiliary rail is completely above said sheet shaping surface portion of
said shaping rail section when said auxiliary rail and said movable
shaping rail section are each at their first position.
13. An apparatus for shaping a glass sheet, comprising:
a support frame;
a shaping rail supported on said frame and having a movable shaping rail
section movable toward said support frame to a first position and away
from said support frame to a second position wherein when the movable
shaping rail section is in the second position the shaping rail has a
sheet shaping surface that conforms in elevation and outline to a final
desired shape of a marginal edge of a glass sheet to be shaped; and
at least one auxiliary rail having a sheet shaping surface, positioned
adjacent the movable shaping rail section of said shaping rail, wherein
said movable shaping rail section has a sheet shaping surface portion
generally corresponding to said final desired shape of a selected marginal
edge portion of the sheet to be shaped, said auxiliary rail is pivotally
mounted for movement relative to said movable shaping rail section between
a first and second position wherein when said auxiliary rail and said
moveable shaping rail section are each in their first position, portions
of said sheet shaping surface of said auxiliary rail are above said sheet
shaping surface portion of said movable shaping rail section and wherein
when said auxiliary rail and said moveable shaping rail sections are each
in their second position, said sheet shaping surface of said auxiliary
rail is below said sheet shaping surface portion of said movable shaping
rail section.
14. A method of shaping a glass sheet by gravity sag bending, including the
steps of:
providing a shaping rail having a movable shaping rail section, the movable
shaping rail section having an upper shaping surface, the movable shaping
rail section movable from a first position to a second position wherein
when the movable shaping rail section is in the second position the
shaping rail has an upper shaping surface having an elevational contour
and outline generally corresponding to a final desired shape of a marginal
edge portion of a sheet to be shaped;
supporting an auxiliary rail adjacent the movable shaping rail section, the
auxiliary rail mounted for movement between a first position and a second
position, the auxiliary rail having an upper shaping surface generally
corresponding to a preliminary shape of a selected marginal edge portion
of the sheet to be shaped, wherein when said auxiliary rail and movable
shaping rail sections are each in their first position portions of said
shaping surface of said auxiliary rail are above portions of said upper
shaping surface of said movable shaping rail section;
positioning the movable shaping rail section in its first position and the
auxiliary rail in its first position;
placing said sheet on said shaping rail with an end portion of the sheet on
said auxiliary rail such that said selected marginal edge portion of said
sheet is supported by portions of said upper shaping surface of said
auxiliary rail and above said upper shaping surface of said movable
shaping rail section;
heating said sheet to its heat softening temperature such that a first
portion of said sheet sags by gravity into contact with portions of said
upper shaping surface of said shaping rail and said selected marginal edge
portion of said sheet contacts said upper shaping surface of said
auxiliary rail, to preliminarily shape said sheet; and
moving said movable shaping rail section toward its second position while
moving said auxiliary rail toward its second position to deposit said
selected marginal edge portion of said sheet onto said movable shaping
rail section so as to allow said selected marginal edge portion of said
sheet to sag into contact with portion of said upper shaping surface of
said movable shaping rail section and allow a sheet to sag to its final
desired configuration.
15. The method as in claim 14 further including the step of providing said
upper shaping surface of said auxiliary rail with a straight elevational
profile.
16. The method as in claim 14 wherein said auxiliary rail is positioned
outboard of said moveable shaping rail section.
17. The method as in claim 14 wherein said upper shaping surface of said
auxiliary rail is above the entire upper shaping surface of said movable
shaping rail section when its auxiliary rail is in said first position.
18. The method as in claim 14 wherein the sheet is one of two sheets and
further including the step of contacting at least a portion of a major
surface of at least one of said sheets with a press face having a sheet
shaping surface generally corresponding to its final desired configuration
of the sheets.
19. A method of shaping a glass sheet by gravity sag bending, including the
steps of:
providing a shaping ring having opposing longitudinally extending rails and
on each end of the rails a movable shaping rail section defined as a first
movable rail section and a second movable rail section, each movable rail
section movable from a first position to a second position wherein when
said movable rails are each in the second position the shaping ring has an
upper shaping surface with an elevational contour generally corresponding
to a final desired shape of a marginal edge portion of a sheet to be
shaped;
positioning an auxiliary rail adjacent each one of the movable rail
sections wherein the auxiliary rail adjacent the first movable rail
section is defined as a first auxiliary rail and the auxiliary rail
adjacent the second movable rail section is defined as a second auxiliary
rail, each of the auxiliary rails having an upper shaping surface with a
straight elevational profile, wherein each of said auxiliary rails are
movable between a first position and a second position said upper shaping
surface of said auxiliary rails is above said upper shaping surface of
said corresponding movable shaping rail section when the auxiliary rail
and the corresponding movable shaping rail section are each in the first
position;
positioning the auxiliary rails in their first position and the movable
rail sections in their first position;
placing said sheet on said shaping ring such that at least first selected
marginal edge portions of said sheet are supported by said upper shaping
surface of said auxiliary rails and
second selected marginal edge portion of the sheet are above said
longitudinally extending rails of the shaping ring;
heating said sheet to its heat softening temperature such that the second
selected marginal edge portions of said sheet sag by gravity into contact
with an upper shaping surface of said longitudinally extending rails of
the shaping ring to impart a preliminarily shape to said sheet; and
moving said auxiliary rails toward their respective second position while
moving the movable shaping rail sections toward their respective second
position to deposit said first selected marginal edge portions of said
sheet onto the movable shaping rail sections to allow said first selected
marginal edge portion of said sheet to sag into contact with upper shaping
surfaces of said movable rail sections and sag to a final desired
configuration.
20. The apparatus as in claim 1 wherein said auxiliary rail has a sheet
shaping surface generally corresponding to a preliminary shape of said
selected marginal edge portion of said sheet.
21. The apparatus as in claim 20 wherein said at least one auxiliary rail
is pivotally mounted at one end.
22. The apparatus according to claim 1 wherein said at least one auxiliary
rail is a first auxiliary rail positioned adjacent the first movable
shaping rail section and further including a second auxiliary rail
positioned adjacent the second movable rail section, said second auxiliary
rail having a sheet shaping surface, positioned adjacent second movable
shaping rail sections of said shaping rail, wherein said second movable
shaping rail section has a sheet shaping surface portion generally
corresponding to said final desired shape of a selected marginal edge
portion of the sheet to be shaped, said second auxiliary rail mounted for
movement relative to said second movable shaping rail section between a
first position, and a second position wherein when said second auxiliary
rail and said second moveable shaping rail sections are in their first
position, portions of said sheet shaping surface of said second auxiliary
rail are above said sheet shaping surface portion of said second movable
shaping rail section and wherein when said second auxiliary rail and said
second moveable shaping rail sections are each in their second position,
said sheet shaping surface of said second auxiliary rail is below said
sheet shaping portion of said second movable shaping rail section.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to sag bending of glass sheets on bending molds and,
in particular, to an apparatus and method for controlling the sag bending
along selected portions of the glass sheets while moving the sheets on
bending molds through a heating lehr.
2. Technical Considerations
In the practice of sag bending to form shaped glass windows for automobiles
and the like, as disclosed in U.S. Pat. No. 4,375,978 to Reese, a glass
sheet is supported on a skeletal bending mold. The shaping rail of the
mold has a shape and configuration similar to that of the shaped glass
sheet at a location slightly inboard of its peripheral edge. The bending
molds are then conveyed in succession through a heating lehr where the
glass sheet is heated to its deformation temperature such that it begins
to sag by gravity until the glass sheet conforms to the configuration of
the shaping rail. After the glass sheet is shaped, the mold is conveyed
through an annealing zone where the glass sheet is cooled in a controlled
manner from its deformation temperature through its annealing range to
anneal the glass sheet. This gravity sag bending technique has been used
to simultaneously shape two glass sheets, or doublets, which sheets are
subsequently laminated together to form an automobile windshield.
As automotive stylists strive for more aerodynamic designs, the windshields
are assuming more complex and deeper bend configurations, which are
increasingly more difficult to form by conventional sag bending
operations. It has been found that in producing shaped glass doublets with
a deep curvature along its center line, because of the amount of heat and
length of time required to achieve such a deep sag, portions of the glass
in the vicinity of the shaping rails are prone to excessive sag bending.
Various arrangements have been developed to assist in controlling the shape
of the glass sheets. In U.S. Pat. Nos. 4,265,650 and 4,894,080 to Reese et
al., the glass sheets are pressed against one press face or between two
opposing press faces. In U.S. Pat. Nos. 4,804,397 to Stas et al. and U.S.
Pat. No. 5,049,178 to Pereman et al., partial presses are used to contact
and press selected portions of the glass sheets. These shaping methods
positively form the sheets to the desired configuration, but because the
press faces contact the glass surfaces, there may be some marking. U.S.
Pat. No. 5,167,689 to Weber controls bending at the corners of glass
sheets supported on an outline mold by sag bending the sheets to a
preliminarily curved configuration and subsequently lifting selected
peripheral portions of the sheet off the curved shaping rails with
additional shaping rails having the final desired elevational
configuration. This arrangement reduces reverse bending at the corners of
the glass sheets but does not address the problem of excessive sag of the
glass near the shaping rails.
It would be advantageous to develop an apparatus and method for forming
glass sheets while controlling excessive deformation of the glass in the
vicinity of the peripheral shaping rails.
SUMMARY OF THE INVENTION
The present invention provides an apparatus and method for a shaping sheet
including a support frame and a shaping rail supported on the frame. The
shaping rail has a sheet shaping surface that conforms in elevation and
outline to a final desired shape of a marginal edge of a glass sheet to be
shaped. An auxiliary rail having a sheet shaping surface which generally
corresponds to a preliminary shape of a selected marginal edge portion of
the sheet is positioned along a section of the shaping rail having a sheet
shaping surface portion which generally corresponds to the final desired
shape of the selected marginal edge portion of the sheet. The auxiliary
rail is mounted for movement relative to the shaping rail section from a
first position, wherein portions of the sheet shaping surface of the
auxiliary rail are above the sheet shaping surface portion of the shaping
rail section, and a second position wherein the sheet shaping surface of
the auxiliary rail is positioned below the sheet shaping surface portion
of the shaping rail section. When the auxiliary rail is in its first
position, it is capable of supporting the selected marginal edge portion
of the sheet above the shaping rail section and preliminarily shaping the
sheet. When the auxiliary rail is in its second position, the sheet
shaping surface portion of the shaping rail section is capable of
supporting and shaping the selected marginal edge portion of the sheet to
the final desired shape.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective cutaway view of a heating lehr showing glass sheets
supported on an outline ring mold incorporating the present invention,
with portions removed for clarity.
FIG. 2 is an enlarged perspective view of a pivoting wing section of the
ring mold illustrated in FIG. 1, with portions removed for clarity.
FIG. 3 is an end view of the pivoting wing section of the ring mold
illustrated in FIG. 1 showing an auxiliary rail in a raised and lowered
position, with portions removed for clarity.
FIGS. 4, 5 and 6 are schematic sectional views of the pivoting section of
the ring mold illustrated in FIG. 1 taken along line A--A at different
stages during a glass sheet sag bending operation, with portions removed
for clarity.
FIG. 7 is an end view of an alternate embodiment of the ring mold of the
present invention, with portions removed for clarity, showing an auxiliary
rail in a raised and lowered position.
FIG. 8 is a side view of another embodiment of the ring mold of the present
invention, with portions removed for clarity, showing an auxiliary rail in
a raised and lowered position.
FIGS. 9, 10 and 11 are schematic perspective views generally corresponding
to FIGS. 4, 5 and 6, respectively, showing the shaping sequence of a sheet
supported on the outline rail of the present invention, with portions
removed for clarity.
DETAILED DESCRIPTION OF THE INVENTION
The invention as discussed herein is presented in combination with a
conventional stop-and-go type heating lehr, wherein the glass sheets are
supported on shaping rails within separate heating chambers that are
sequentially conveyed through the lehr to heat and shape the glass sheets,
in a manner well known in the art. It should be appreciated that the
present invention may be incorporated into the sag bending operation of
glass sheets using other types of heating lehrs, e.g. conventional
tunnel-type lehrs.
In the process of shaping glass sheets by gravity sag bending, one or more
glass sheets G are positioned on a carrying frame 10 at a loading station
(not shown) and conveyed through a heating lehr 12, where they are heated
to their heat-softening temperature and allowed to sag by gravity to a
desired shaped configuration. After shaping, the sheets G and frame 10 are
conveyed through annealing and cooling zones of the lehr 12 to minimize
stresses in the glass and set the glass shape. Referring to FIG. 1, a
conveyor comprised of a plurality of stub rolls 14 disposed in
transversely opposing, longitudinally spaced relation extend the entire
length of the lehr 12 and defines a path of movement of frame 10 along a
longitudinal reference line through the lehr. Each stub roll 14 is mounted
on a shaft that extends through a side wall of the lehr 12 and is
connected to a conveyor drive means (not shown). The conveyor may be
divided into a number of sections, each driven from its own drive means,
or the conveyor sections may be driven from a common drive through
clutches, in any manner well known in the art.
Although not limiting the present invention, the frame 10 illustrated in
FIG. 1 includes a ring mold 16, similar to the mold disclosed in U.S. Pat.
No. 4,626,267 to Reese and U.S. Pat. No. 4,804,397 to Stas et al., which
teachings are herein incorporated by reference, having a sheet shaping
surface 18 that conforms in elevation and outline to a final desired shape
of the marginal edge of the glass sheets G to be shaped. Frame 10 may
include other insulating structures (not shown) which enclose the frame 10
and isolate it from adjacent frames. In this particular embodiment, mold
16 is an articulating mold with pivoting end sections; however, it should
be appreciated that the present invention may be used in combination with
a non-articulating ring mold. The mold 16 is provided with opposed,
spaced-apart central rails 20 (only one shown in FIG. 1) and two pivoting
end sections 22, each of which includes side rails 24 and an end rail 26.
Each end section 22 is supported by an outrigger 28 positioned below the
corresponding rails 24 and 26. The outrigger 28 extends outward of the end
sections 22 towards a pivot on post 30 and is attached to a weighted lever
arm 32. As the glass sheets G supported on ring mold 16 are heated, the
lever arm 32 moves downward under the force of gravity against the
lessening opposing force of the glass sheets G as they become heat
softened to pivot the end sections 22 upward to a closed position as shown
in FIG. 1. In this closed position, rails 20, 24 and 26 form shaping
surface 18 and the glass sheets G sag by gravity into contact and are
shaped by surface 18 slightly inboard of their periphery.
The following discussion is directed towards using an additional shaping
rail on one of the pivoting end sections 22 to control glass shape during
a gravity sag bending operation, but it should be understood that, if
required, the additional rails may be similarly positioned along portions
of center rails 20 or end section rails 24 and 26 at the opposite end of
mold 16.
Referring to FIG. 2, end section 22 of mold 16 further includes an
auxiliary rail 34 which extends along and is positioned adjacent to end
rail section 26 of end section 22. Auxiliary rail 34 is supported on frame
10 to move between a raised position wherein the upper sheet shaping
surface 36 of auxiliary rail 34 is generally positioned above the upper
sheet shaping surface 38 of adjacent rail 26 as illustrated in FIGS. 1, 2
and 3, to support and preliminarily shape a marginal edge portion 40 of
the glass sheets G, and a lowered position wherein surface 36 of auxiliary
rail 34 is positioned below surface 38 of adjacent end rail 26 as
illustrated by phantom lines 42 in FIG. 3 such that rail 26 can support
and shape marginal edge portion 40 to its final desired configuration
during a portion of the sag bending process. In particular, the
elevational profile of shaping surface 36 is configured to have a
curvature which is less than that of surface 38 of adjacent rail 26 so
that as long as marginal edge portion 40 is supported on auxiliary rail
40, it cannot sag to its final configuration. By delaying the final sag
bending of the sheets G, and, in particular, marginal edge portion 40 and
those portions of the sheets in the vicinity of edge portion 40 within end
section 22, until late in the sag bending operation, as will be discussed
later in more detail, the amount of time available for those areas of the
glass sheets G to sag by gravity is reduced so that the sheets cannot sag
excessively in these critical areas. Although not limiting in the present
invention, in the particular embodiment illustrated in FIGS. 1-3, shaping
surface 36 of auxiliary rail 34 has a straight profile, i.e. there is no
vertical curvature along its length and is positioned so that it is
aligned slightly above the highest points of adjacent rail 26.
Auxiliary rail 34 may be moved from its raised position to its lowered
position either by gravity or a mechanical or electro-mechanical device.
Without limiting the scope of the present invention, FIGS. 2 and 3
illustrate one embodiment of a gravity-type arrangement. More
specifically, end 44 of rail 34 is mounted to pivot about post 45. A
bracket 46, which includes a ledge 48, is pivotally secured to outrigger
28 or a guide 50 of pivoting section 22. When in its raised position, rail
34 is supported at one end by post 45 and its opposing end is seated on
ledge 48. At a predetermined time during the glass sheet sag bending
process, bracket 46 is pivoted away from rail 34 causing the rail 34 to
move off ledge 48 and slides downward, as shown by phantom lines 42 in
FIG. 3, pivoting about post 45. Guide 50 maintains auxiliary rail 34's
position generally along adjacent rail 26. In the particular embodiment
illustrated in FIG. 2, guide 50 includes a plate 52 with a slot 54 through
which rail 34 extends and slides along.
Although not limiting in the present invention, the pivoting action of
bracket 46 occurs when end section 22 of mold 16 pivots upward a
predetermined amount. More particularly, referring to FIGS. 4 through 6,
arm 56 extends from bracket 46 and includes a pivoting rod 58 that extends
through a portion of frame 10. Stop 60 is secured to rod 58 such that when
end section 22 of mold 16 is pivoted downward to an opened position, the
stop 60 is spaced from frame 10, as illustrated in FIG. 4. As the glass
sheets G supported on rails 20, 24 and 34 are heated and softened,
pivoting end section 22 begins to rotate upward, as indicated by arrow 62
in FIG. 5, to slowly obtain the final desired elevational contour of the
sheet. Bracket 46 moves with section 22 as it pivots and continues to hold
rail 34 in its raised position as shown in FIG. 5. As end section 22
pivots, rod 58 moves upward, moving stop 60 closer to frame 10. When end
section 22 has pivoted upward a predetermined amount, stop 60 will contact
frame 10. As end section 22 continues to pivot upward, bracket 46 is
prevented from maintaining its orientation relative to rail 34 and is
forced to pivot, as indicated by arrow 64, which results in rail 34
falling off ledge 48 and dropping to its lowered position, as illustrated
in FIG. 6 and depositing the sheet onto end rail 26.
Although in the embodiment of the invention illustrated in FIGS. 1-3,
bracket 46 is positioned at one end of rail 34; it should be appreciated
that it may be positioned at any other location along rail 34, for
example, at its center. It should be further appreciated that other types
of devices may be used to move rail 34 from its raised position to its
lowered position. For example, bracket 46 may be replaced with a linear
actuator, such as an electric motor, ball screw, electric motor, or the
like, to raise and lower one end of rail 34.
It is also contemplated that rather than pivotally mounting the auxiliary
rail 34 at one end and using a support device to move its opposing end,
the rail 34 may be vertically reciprocated between its raised and lowered
positions. More specifically, referring to FIG. 7, opposing ends of rail
34 may be supported by linear actuators 66, as discussed above, to move
both ends of rail 34 upward to its raised position and downward to its
lowered position, as indicated by phantom lines 68. These types of
actuators may be linked to a controller (not shown) which controls the
raising and lowering of rail 34 during the gravity sag bending operation.
It is further contemplated that rather than vertically reciprocating rail
34, the rail 34 may be moved from its raised to lowered position by a
pivoting action. More specifically, referring to FIG. 8, rail 34 may
include additional sections 70 (only one shown in FIG. 8) which are
pivotally mounted to frame 10 so that rather than simply dropping from its
raised to lowered position, rail 34 and additional sections 70 rotate away
from adjacent rail 26, as indicated by phantom lines 72. The rail 34 and
section 70 may be raised and lowered in a manner as previously discussed.
As rail 34 moves from its raised to lowered position, marginal edge portion
40 of the glass sheet G is transferred from the upper shaping surface 36
of auxiliary rail 34 to the upper shaping surface 38 of rail 26. As
discussed earlier, the movement of rail 34 to its lowered position may
occur at any desired time during the sag bending cycle. However, in
determining when auxiliary rail 34 may be lowered, it should be remembered
that there must be sufficient time after the glass sheets G have been
transferred from rail 34 onto rail 26 for the glass G to sag by gravity
into contact with shaping surface 38 of rail 26 and assume its final
configuration. More specifically, at a sag bending temperature of between
about 1060 to 1250.degree. F. (571 to 677.degree. C.), it is estimated
that it will take approximately 10 to 20 seconds for the glass G to sag
into contact with rail 26 after being deposited thereon, depending on the
depth of bend provided by the shaping surface 38. In addition, care must
be taken not to allow for excessive sag bending in those areas inboard of
rail 26 after marginal edge portions 40 have sagged into contact with
shaping surface 38. It is believed that rapid downward movement of
auxiliary rail 34 from its raised to lowered position may accelerate the
final shaping of the marginal edge portion 40 from their preliminary shape
to its final desired shape.
In operation, the ring mold 16 of the present invention shapes the sheets
first in one direction to preliminarily shape the sheets generally in the
longitudinal direction and subsequently in a second direction to impart a
transverse curvature and shape the sheets to their final desired
configuration. More specifically, end sections 22 of the ring mold 16 are
pivoted downward and auxiliary rails 34 (one on each section 22) are moved
to their raised position, as shown in FIGS. 4 and 9, either manually or by
an automatic rail positioning arrangement. Glass sheets G (only one shown
in FIGS. 4-6 and 9-11) are positioned on the ring mold 16 and supported on
rails 34 and end sections 74 of side rails 20. As the sheets are heated,
they soften and sag by gravity. Marginal edge portions 76 along the
longitudinal sides of the glass sheets G sag into contact with and are
shaped by center rails 20 and rails 24 in end section 22 as weighted arms
32 (shown only in FIG. 1) pivot each end section 22 upward, as shown in
FIGS. 5 and 10. The marginal edge portions 40 of the glass sheets G are
supported on auxiliary rail 34, which is initially positioned above rail
26 of end section 22 and remain undeformed. As a result, the glass sheets
G initially deform to assume their longitudinal curvature, i.e. a
generally cylindrical curvature from one end section 22 to the other.
During this preliminary shaping, there may be some transverse sag bending
of the glass, i.e. between the center rails 20, but transverse sag bending
of the sheets G is limited because the shaping surface 36 of each
auxiliary rail 34 is configured to limit sag bending of marginal edge
portions 40 of sheets G immediately inboard of auxiliary rails 34, as
shown in FIGS. 5 and 10. At the desired time in the bending cycle, rails
34 are lowered, depositing marginal edge portions 40 onto rails 26 of end
sections 22, as shown in FIGS. 6 and 11. The glass sheets G continue to
sag by gravity for the time required by the marginal edge portions 40 to
contact shaping surfaces 38 of rail 26 and complete the transverse shaping
of the glass G in pivoting sections 22. After shaping is completed, the
frame 10 and shaped glass sheet G are conveyed through the annealing and
cooling sections (not shown) of lehr 12 where the glass sheets G are
controllably cooled. The shaped sheets G are subsequently removed from the
mold 16 for further processing.
During the sag bending operation, additional sheet shaping arrangements may
be used to further deform the sheets. More specifically, partial or full
surface press faces may contact the upper and/or lower major surfaces of
the glass sheets G to contact and shape selected portions of the glass to
a desired configuration, for example, as disclosed in U.S. Pat. No.
4,804,397. When additional pressing molds are used in combination with an
articulating ring mold as disclosed herein to shape the glass, it is
desirable to incorporate a locking device into the pivoting end sections
22 of mold 16 so that the end sections 22 do not rotate downward when the
glass G is contacted and pressed to shape, as disclosed in U.S. Pat. No.
4,804,397.
As discussed earlier, in the embodiment of the invention illustrated in
FIGS. 1 and 2, auxiliary rail 34 is a straight rail with a straight sheet
shaping surface 36 positioned outboard of rail 26 and is moved vertically
from its raised to lowered position. It is contemplated that the position
and shape of the rail may be modified. For example, auxiliary rail 34 may
extend only along a portion of rail 26 so that it does not support the
entire marginal edge 40 of the sheets G. In addition, auxiliary rail 34
may be positioned inboard of rail 26 rather than outboard. Furthermore,
although it is preferred that sheet shaping surface 36 of auxiliary rail
34 be positioned above sheet shaping surface 38 of rail 26 when rail 34 is
at its raised position, it is contemplated that surface 36 may be
positioned above only a portion of surface 38 so that marginal edge
portion 40 of glass sheets G is supported on and preliminarily shaped by
both the auxiliary rail 34 and rail 26. Auxiliary rail 34 may also be
curved horizontally to conform to the horizontal contour of adjacent rail
26.
As discussed earlier, although it is preferred that the elevational contour
of sheet shaping surface 36 of auxiliary rail 34 be straight in order to
control sag bending in the side portions of the glass sheets G, especially
in the vicinity of the marginal edge portions 40. However, it is
contemplated that the surface 36 may be curved, provided that its
curvature is less than the final desired contour of surface 38 of adjacent
rail 26, i.e. it has a larger radius of curvature. For example, surface 36
of auxiliary rail 34 may have a radius of curvature on the order of about
177 inches (about 450 cm), while surface 38 of adjacent rail 26 has a
radius of curvature on the order of about 89 inches (about 225 cm).
Because surface 36 of rail 34 is "flatter" than surface 38 of adjacent
rail 26, auxiliary rail 34 can preliminarily shape marginal edge portion
40 and allow some preliminary sag bending in the vicinity of marginal edge
portions 40 during the majority of the sag bending operation and surface
38 of adjacent rail 26 can shape marginal edge portion 40 and the
remaining portions of the glass sheets G to their final desired shape
during the latter portion of the sag bending operation.
The present invention controls excessive gravity sag bending in glass
sheets by limiting the amount of glass sag at selected areas of the glass
sheets during a portion of the sag bending operation. The glass sheets are
preliminarily formed about one axis and subsequently formed about a second
axis. This is accomplished by allowing the opposing longitudinally
extending marginal edge portions 74 of the glass sheets G to sag into
contact with opposing rails 20 and 24 while supporting the transversely
extending marginal edge portions 40 of the glass sheets G on auxiliary
rails 34. As a result, the sheets G assume their general longitudinal
curvature. Rails 34 are thereafter lowered to allow edge portions 40 to be
supported by and sag into contact with rails 26 of end sections 22
facilitate sag bending of the glass sheets in the transverse direction,
especially in the vicinity between rails 24 of end sections 22, and
complete the shaping of the glass. By maintaining the marginal edge
portions 40 in a generally flat configuration and delaying the transverse
sag bending in these selected areas until late in the sag bending process,
the contoured shape of the glass in the pivoting sections 22 is controlled
and excess sag bending is minimized. In addition, reducing the excessive
sag bending by controlling the rate and manner in which the glass is
shaped will also reduce distortion in the glass sheet due to undesired
reverse bending of the sheet, especially at its corners.
The invention described and illustrated herein represents a description of
illustrative preferred embodiments thereof. It is understood and various
changes may be made without departing from the gist of the invention
defined in the claims as follows.
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